The present invention relates generally to tracking control systems in magnetic recording and/or reproducing apparatuses and more particularly to a system which, by controlling the rotational phase of reproducing rotating magnetic heads, accomplishes tracking control in a manner such that the magnetic heads can trace accurately along a track on a magnetic tape.
In recent years, in magnetic recording and/or reproducing apparatuses such as video tape recorders (VTR) of the helical scan type for home use, there has been a trend toward even higher densities of recording and reproducing, aided by improvements in magnetic tapes. For example, by reducing the tape speed and track pitch to approximately 1/3, for example, of their values as compared to the case of the conventional recording and/or reproducing capacity of 2 hours, recording and reproducing of 6 hours can be carried out. Such long-duration recording and/or reproducing techniques are being reduced to practice. However, in the VTR for home use, in which the tape travel system is simplified in order to lower the cost, it is difficult to reproduce a magnetic tape having a reduced track pitch as mentioned above while positively maintaining the required tracking precision.
Furthermore, in a magnetic recording/reproducing apparatus capable of recording/reproducing for 2 hours, it is necessary to manipulate a tracking knob in order to cause the magnetic head to undergo accurate tracking along a track of the magnetic tape when interchanged reproduction is performed with another apparatus. That is, in the case where there are (1) differences in the position of the control head, (2) differences in the height of the video head, and (3) skews in the video track, between the recording and reproducing apparatuses, optimal tracking state is not obtained, and hence maximum output cannot be obtained at the time of this interchanged reproduction.
For example, in the case where the distance L from the position where a video head which is mounted on the rotary drum begins to make contact with the magnetic tape to the position of the control head is longer than a standard value in the recorder, the tracking phase deviates. In this case, a control pulse is recorded by the control head at the lower edge of the magnetic tape. In a magnetic recording and/or reproducing apparatus capable of carrying out recording and reproducing of 6 hours, for example the recording interval of the control pulse is 0.37 mm., which is approximately 1/3 of the 1.11 mm, obtained in the case of a conventional recording and reproducing of 2 hours.
In the case where the above mentioned distance L is not coincident with the standard value, it is necessary to adjust the tracking knob to delay the reproducing control signal by a required time to thereby carry out normal tracking. However, adjustment of the tracking knob requires an operation in which, as the reproduced picture is observed, the knob is finely adjusted in a manner such that noise is not generated, and this manipulation is complicated.
Furthermore, while the rotational control of the rotary drum and the rotating magnetic heads carried out by means of a drum servo-control by reproducing the above mentioned control pulses accomplishes a control function of a degree such as to maintain the relative positions of the corresponding positional relationship between each track and the rotating video heads, this rotational control, in the prior art, has not accomplished the function of a so-called tracking control.